1. Field of the Invention
The present invention relates to a method and apparatus to optically recognize recorded information and more particularly to one in which an image signal derived from the scanning of information is filtered for the precise recognition of information.
2. Description of the Prior Art
Information encoding and decoding techniques are well known in the art. According to one of these techniques, the information is recorded on an object in the bar code form, for example, to be optically recognized. An illumination light and a light responsive sensor are arranged in this optical recognition system in such a manner that the former projects the light onto the object and the latter receives the reflected light from the object to generate an image signal which represents the recorded information. This image signal is then processed electrically for recognizing the recorded information. It has been a great disadvantage, however, that the light responsive sensor is likely to generate an image signal which includes a periodic noise signal when the light source is energized by a commercial alternating current electric power of rather low frequency. This is because the illumination light from the light source fluctuates in accordance with the electric power and the density of the reflected light also fluctuates in accordance therewith. This disadvantage still occurs when the object is supplied with the light from other than the light source.